Inflatable nozzle plug for reaction engine



July 2, 1968 c. PEL. ETAI. 3,390,529

INFLATABLE NOZZLE PLUG FOR REACTION ENGINE Filed Nov. 29, 1966 UnitedStates Patent O 3,390,529 INFLATABLE NOZZLE PLUG FOR REACTION ENGINECornelius Pel, Encino, and Heinrich Epple, Gardena, Calif., assignors tothe United States of America as represented by the Secretary of the AirForce Filed Nov. 29, 1966, Ser. No. 597,811 4 Claims. (Cl. 60-271)ABSTRACT F THE DISCLOSURE A closure arrangement for sealing the exhaustopening of a reaction engine comprising an inflatable flexible materialhaving a fluid drain portion and a scuttle device for rupturing saidmaterial.

This invention relates to a novel closure arrangement for plugging theexhaust opening of a reaction engine. More particularly, the inventionis concerned with providing an inflatable structure for covering thenozzle opening of a reaction engine such as a rocket, the structurebeing jettisonable in response to an electrical signal which causestearing to occur in a prearranged pattern followed by separation fromthe carrying vehicle.

In order to protect the interior of reaction engines, such as rocket orjet engines, from the effects of hot gases emitted by other auxiliarymotors mounted and operating nearby, it is desirable to seal off thenozzle section of the main engine while the other motors are inoperation. The gases, if allowed to enter the combustion chamber throughthe nozzle section` could adversely effect the initial operation of themain engine. Various covering means, such as spring ejected coverplates, have been used to plug the nozzle of the main engine, but nonehave been entirely satisfactory because of the possibility of damage toother portions of the vehicle upon jettisoning of a cover plate type ofplug and also the relatively heavy weight of the solid plug.

The present invention provides a novel closure arrangement made from asuitable flexible material such as nylon which can be inflated to form aclose tting seal to prevent the hot gases from other nearby motors fromentering the main engine through the nozzle section.

Means are provided for draining away any oxidizer which may leak intothe outer section of the nozzle. Also, the present invention can bejettisoned without damaging adjacent structures of the engine and aconsiderable weight saving is accomplished by employing a thin flexibleinilated structure rather than the solid, presently used, cover plate.

Accordingly, it is an object of the invention to provide a novel closurefor plugging the nozzle of a rocket engine. The closure is fabricatedfrom a light-weight material and is inflatable so as to conform to anydistortions in the nozzle section.

Another object of the invention is to provide an inflatable nozzle plugfor a reaction engine which is jettisonable by tearing in a prearrangedpattern in response to an electrical signal and parting from thecarrying vehicle without causing damage thereto.

Still another object of the invention is to provide an inflatable nozzleplug having a slanted upper extremity to permit drainage of leakingoxidizer to a low point from where it can be carried away to the outsideatmosphere.

A further object of the invention is to provide an inilatable nozzleplug which has the general geometric configuration of a truncatedconical structure, the side area of which substantially conforms to theinner surface of the nozzle section.

A still further object of the present invention is to pro- 3,390,529Patented July 2, 1968 rice vide an inflatable nozzle plug constructed ofa fabric material that is coated with neoprene or polyurethane having aportion coated with Teflon or Kel-F so as to be resistant to the effectof the oxidizer (nitrogen tetroxide).

These and other objects, features and advantages will become moreapparent after considering the following detailed description taken inconjunction with the annexed drawing and appended claims.

In the accompanying drawing, there is shown an elevation view partly incross section and fragmentary of a reaction engine inflatable nozzleplug -according to the invention.

Referring now to the drawing, the novel nozzle plug illustrated thereinis shown positioned in the nozzle section 13 of a reaction motor. Withinthe lowermost section of the nozzle 13, there is poistioned aninflatable closure structure generally designated by the characterreference numeral 15. Geometrically, the structure 15 resembles atruncated cone with the inner base 17 slightly `slanted to permitdrainage of leaking oxidizer toward a drain tube 19 through which it canbe evacuated to the outside.

The inner base area 17 as well as the walls 21 may be made of nylonfabric coated with neoprene or polyurethane. A very thin coating ofTeflon or Kel-F may be added over the previously described coating inthe inner base area 17 so that any oxidizer coming in contact therewithwill not cause deterioration of the structure. The outer base areacomprises an end disk 23 which serves to externally seal the nozzle andthe reaction motor combustion chamber. The heat resistant material suchas Gengard 44 having a thickness of one-fourth inch is used to fabricatethe end disk 23 which forms outer base area. This material, in additionto being flexible and impervious, is also heat resistant and will endurea heat flux of 10 B.t.u. per second per square foot for a duration ofseconds. A fill valve 25 having a protruding fill hose 27 is attached onthe side of the inflatable structure and extends into the interiorthereof for the purpose of pressurization of the structure once it is inposition in the nozzle 13.

Atthe inner base area 17, an overpressure valve 29 is positioned tomaintain a continuous overpressure of 5 p.s.i. against ambient pressure.Adjoining the Valve 29 is a scuttle device 31 which, upon receipt of anelectrical signal from the signal control 33, will puncture theinflatable structure and will cause the inner base area 17 to tear alongseveral frangible radial seams. Based on a continuous overpressure of 5p.s.i. inside the inflabtable structure, and assuming a coefficient offriction of .69 between the rubberized nylon and the inner nozzlematerial, sufficient friction is created to retain the bag in place whena 3 g acceleration and a negative base pressure of 3 p.s.i.g. shouldoccur simultaneously.

Once an electrical signal from the signal control 33 has been receivedby the scuttle device 31 causing the inflatable structure 15 to rupture,the pressurized gas previously contained within this structure will nowoccupy the entire volume forward of the end disk 23 causing the pressureto drop to approximately 2.25 p.s.i. which, because of leakage throughthe drain tube 19, will decrease even further. With pressureequalization, the friction between the inflatable structure 15 and thenozzle 13 will cease to function as the retaining means and the lack ofexternal pressure against the outer base area will cause the end disk 23to be jettisoned outward. The time interval between receiving theelectrical signal from the signal control 33 and -accomplishing pressureequalization behind the end disk 23 has been estimated to be in theorder of 80 milliseconds.

As seen from the preceding description of a specific embodiment of theinvention, the inflatable nozzle plug prevents contaminants fromentering through the exhaust section of the engine. The flexibility andease of installation of the iniiatable structure makes possible theattachment of the plug to the nozzle section of a reaction engineirrespective of -any minor irregularities in the shape of the dischargeopening. Also, the closure according to the invention, is unusuallylight in weight, can be installed and removed without damage to theengine, and can be manufactured relatively inexpensively from readilyavailable materials.

Although the invention has been illustrated in the accompanying drawingand described in the foregoing speciiication in terms of a preferredembodiment thereof, it should be understood that the invention is notlimited to this embodiment or to the particular uses mentioned. It willbe apparent to those skilled in the art that the invention may also beemployed as a closure to protect the inlet and/or the exhaust openingsof jet and rocket engines from the adverse effects of dust, moisture,and foreign particles which may enter therein during the storage orservicing of the engine. Various changes, alterations, modications, andsubstitutions, particularly with respect to the construction details canbe made in the arrangement of the several elements without departingfrom the spirit and scope of the appended claims.

Having thus set forth and disclosed the nature of our invention, what weclaim and desire to secure by Letters Patent of the United States is:

1. An inflatable closure plug for covering the nozzle opening of areaction engine, said closure plug comprising a iiexible hollowstructure generally shaped in the form of a truncated cone, saidstructure being dimensioned to iit closely within and to conformsubstantially to the geometric configuration of the inner wall lowerportion of the nozzle section of the reaction engine, lan end disc ofpartially heat and pressure resistant material positioned across thebase of said nozzle section forming the outer base of said hollowsection, means for iniiating said hollow structure to a slightoverpressure, means for controlling the overpressure in said structure,scuttle means on the inner base of said infiatable structure forinitiating the deflation and subsequent destruction and release of thestructure from the carrying vehicle after the reaction engine starts tooperate, the further operation of said engine causing the destruction ofsaid end disc because of the lack of support by the inflatable structureand the carrying away of the `destroyed end disc along with the inatablestructure.

2. The inflatable closure plug defined in claim 1 wherein the exiblehollow inflatable structure being truncated conical in geometricconfiguration includes a downwardly slanted inner base surface, and adrain tube in communication with the outer atmosphere, said drain tubebeing positioned between the outer wall of the inatable structure andthe inner nozzle wall, the open upper end of said drain tube beingdisposed to receive any liquid material which runs down the slantedinner base area.

3. The inatable closure plug delined in clairn 1 wherein the flexiblehollow inflatable structure includes a plurality of prearranged radiallyseamed weakened areas to facilitate and control the rupture patternduring the destruction of said inflatable structure.

4. The inatable closure plug defined in claim 1 wherein the flexiblehollow inflatable structure is fabricated of a fabric material, saidfabric being coated with a rubberlike substance to produce asubstantially air-tight arrangement, the outer surface of the inner basebeing further coated with a substance to protect the inflatablestructure from corrosive effects of liquids which may come in contacttherewith.

References Cited UNITED STATES PATENTS CARLTON R. CROYLE, PrimalyExaminer.

